There is a perceived need for food containers which have the ability to protect ingredients packaged therein against loss of essential oils and/or flavorings, such as fruit or citrus juices, beverages, and the like. Paperboard coated with polyethylene has been tried for this purpose, but it falls short of providing an acceptable container because polyethylene absorbs, or permits the migration of, an appreciable amount of the essential oils and/or flavorings. The loss of these oils and/or flavorings results in loss of taste and aroma of the juice, such as orange juice.
U.S. Pat. No. 3,120,333, for example, discloses the well-known gable-top milk carton prepared from a laminate of paperboard extrusion-coated on both sides with polyethylene; the polyethylene is employed as a moisture barrier and is in contact with the milk.
U.S. Pat. No. 3,464,546 discloses a multi-layer container for latex and oil based paints wherein the inner layer is an oxygen barrier resin, such as a vinylidene chloride polymer.
U.S. Pat. No. 3,560,227 discloses high barrier coated papers which include, inter alia, the use of a vinylidene chloride polymer sandwiched between two layers of polyethylene which are adhered to a paper base, said to be useful as a barrier for oxygen and water vapor.
The use of polyethylene film as a packaging material is well known, including packages which employ a multi-layer construction wherein the polyethylene is the layer which is in direct contact with packaged ingredients. It has been generally believed that a barrier layer (such as a vinylidene chloride polymer) in a multi-layer construction is effective as a barrier, even though it is not the layer in contact with the packaged ingredients; this belief is well-founded when considering only the barrier properties for oxygen and water vapor. We have found, however, that when a barrier for the essential oils and/or flavorings in juices or beverages is needed, then the halopolymer, such as a polymer of vinylidene chloride, needs to be the layer in direct contact with the juices and beverages in order to be efficient. If there is a layer of polyethylene between the halopolymer and the packaged juices and beverages, then the polyethylene absorbs a significant amount of the essential oils and/or flavorings and having the halopolymer behind the polyethylene does not prevent the absorption into the polyethylene. The loss of essential oils and/or flavorings results in loss of flavor and aroma and the storage time (shelf-life) is considerably shortened if polyethylene is the layer in contact with the juices and/or beverages.
Of importance among the esssential oils and/or flavorings are terpenes. Limonene is a cyclic terpene which can be dextro or laevo; d-limonene is an essential oil found in citrus fruits; it provides at least a large percent of the distinctive flavor and aroma of citrus fruits. Other aroma/flavoring ingredients found in nature's products are included within the meaning of the expression "essential oils and/or flavorings". For instance, vanillin (the aroma and flavor constituent of vanilla bean extract), eugenol (the chief constituent of oil of cloves) and isoeugenol (in nutmeg oil) are among the flavorings added to food products such as baked goods and dry cereals and the like.
A technique has been developed (Journal of The A.O.A.C., Vol. 49, No. 3, 1966, p. 628) which measures the approximate concentration of d-limonene in orange juice as a measure of the essential oils and flavorings. A loss of d-limonene upon storage causes a perceptible change in taste and aroma; this loss of d-limonene and change in taste and aroma is undesirable and should be avoided.
It is an object of this invention to provide a laminate material for making containers for foods, juices and beverages which contain essential oils and/or flavorings. A further object is to provide in such containers an inner-wall barrier layer which substantially prevents migration of essential oils and/or flavorings from foods, juices or beverages stored therein.